Since the oil embargo of 1973, periodic fuel shortages in spite of steadily increasing prices for petroleum-derived products have dramatically changed the economics of automobile operation and ownership throughout the world. The automobile industry in the United States reacted to government regulation and the changing market with prolonged programs for down-sizing and weight reduction of existing marques, introduction of new models similar to the smaller European and Japanese designs, and evaluation of existing and new materials as possible substitutes for the traditional heavy materials, notably steel, rubber and glass.
Although evolutionary in nature, the recent changes in design and manufacture of American automobiles are unprecedented in number and frequency. The cost in product quality and corporate cash flow problems to effect such changes has been substantial and no doubt will be studied by engineers and economists for many years.
Two problems basic to the design of conventional automobiles have interfered with the evolution of a successful economy car. First, physical compromises are such that an automobile designer ordinarily must sacrifice either performance or comfort to achieve operating economy. Second, a lightweight vehicle, which may be more energy-efficient than a heavy one, may actually cost more dollars than a heavier vehicle because of the necessity for using exotic materials, unorthodox manufacturing methods, and specially-designed components. As a result of the balanced approach currently being taken by the automotive industry among cost, performance and comfort, the automobile market has shown a remarkable ambivalence toward the modern "economy car" in spite of high fuel prices and the nearly universal expectation of still higher fuel prices in the future.
As used herein, the terms vehicle, automobile, and the like may be used interchangeably and in general are intended to include any self-propelled or passive load-transporting device the same as or similar to the following machines: automobiles, vans, pickup trucks, station wagons, mobile homes, ambulances, etc.; trucks; trailer or wagons; recreational vehicles, such as golf carts, snowmobiles, etc.; medical equipment, such as wheelchairs, hospital carts, etc.; aircraft taxiing or ground propulsion and/or braking systems; mobile machinery of any kind, including agricultural, mining, lawn, garden, forestry, etc.
Weight is a major problem in conventional vehicles. Often the weight and strength of frame and chassis members must accommodate the large force concentrations when the standard four point suspension, i.e. with wheels at each of the four corners of the vehicle, is used. Vehicles with drive belts or drive treads, such as a bulldozer, still have principal vehicle support points at opposite extremities or corners. Another disadvantage with such belt driven or tracked vehicles is the generally reduced maneuverability relative to conventional vehicles. Moreover, in conventional vehicles rugged functional mechanisms of large mass, e.g. tires, wheels, brakes, steering linkages and joints, bearings, wheel spindles, axles, differential gearing, springs, shock absorbers, and drive shaft, are mounted at locations where they tend to behave collectively like linear harmonic oscillators, especially as the vehicle passes over uneven road surfaces. Such oscillations cause considerable displacement of the vehicle body itself from a smooth trajectory causing passenger discomfort and excessive wear, and the displacements become progressively more abrupt as the vehicle weight decreases or as the suspension spring constants, unsprung weight, and unused payload capacity increase.